1. Field of the Invention
The present invention relates to systems and methods for preventing unauthorized reception of media programs and in particular to a method and apparatus for verifying the contents of a memory storing instructions for granting access to such memory programs.
2. Description of the Related Art
One method to assure the security of the media programs broadcast over such systems is through the use of a conditional access module (CAM) removably coupled to the media program receiver. The media programs are transmitted and received in encrypted form, and a decryption engine disposed in the CAM is used to decrypt such media programs so that they can be presented to the viewer. CAMs typically include a microprocessor, a memory storing microprocessor instructions, and an input/output (I/O) module.
If the encryption operations in the CAM are compromised, unauthorized access to the media programs may result. One of the simplest and most prevalent form of attack against microcontroller components uses external means using the system input/output interface. This can reveal the contents of the microprocessor memory, exposing it's secure data or functionality. This information can be used to determine and ultimately subvert or bypass important microprocessor functions.
What is needed is a system and method that increases the difficulty of such attacks, reduces the probability that such attacks will ultimately prove successful, and to limit the general applicability of any information derived from such attacks. The present invention satisfies that need.